This invention relates to binoculars which can be worn on a user's head without the need for holding the binoculars by hand and which have independently adjustable eyepiece devices to facilitate adjusting the focus and eye relief and separately adjusting the focus for a single eye.
The focus adjustment of conventional binoculars is often done by taking the use of screw-thread transmission to control the distance between the eyepiece and objective lens. So far as the manufacturing technique is concerned, the screw-thread dies-making technique is difficult, so that the manufacturing cost of the dies is higher than that of dies in general. In order to make a reasonable profit, such cost has to be reflected in the price to the consumer resulting in increased prices he must pay. For a pair of binoculars for leisure which do not need maximum precision, such a cost is economically important.
In addition, generally speaking, among an absolute majority of people, the sight of two eyes of anyone differs from each other, but the focus adjustment of conventional binoculars is performed synchronously for one's two eyes but cannot be done separately for either the left or right eye. Therefore, for someone who has a large sight difference between his or her two eyes, conventional binoculars cannot meet the user's requirements.